Experiment 1: IR Unknown/Spectroscopy Assignment FOURIER-TRANSFORM INFRARED SPECTROSCOPY

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Purpose: The purpose of this experiment is to practice the usage of infrared spectroscopy and to identify the unknown compound # 53 using Fourier-Transform Infrared Spectrometer. From the IR spectroscopy, specific functional group peaks are noted and used to aid the identification of the unknown organic compound. Furthermore, in this experiment, another unknown will be given and researched upon its spectral data.

Main Reaction: There is not reaction carried out in this experiment.

Table of Physical Properties: (This is for both Part I and Part II)

Source: www.chemfinder.com and www.aist.go.jp/RIODB/SDBS/menu-e.html


molar mass

mp (°C)



density (g/mL) Miscellaneous: concentration, solubility, safety hazards





1.045 *Almond smell

*Yellow-orange color

*<0.01g/100mL @ 19.5°C

*Combustible & eye irritant

IR Peaks:

*2732 & 2814 (pair of small peaks: aldehyde C-H)

*1709 (strong C=O)





0.867 *Colorless Liquid

*0.03g/L @ 20°C


IR Peaks:

*1497 (Strong: C=C aromatic bond)

*2967 (Strong: aromatic C-H bond)

Part I.

Unknown #53

Preparation: Before collecting any data, the selected unknown sample was observed in its color and smell. Then, the Fourier-Transform Infrared Spectrometer detector was cleaned with CH2Cl2 and wiped dry. Then a background IR was taken to aid the clarity of sample IR. The background IR was not added to window to prevent overlapping of the actual sample IR and the air IR. Around 1 drop of unknown liquid sample was then placed on the detector using a capillary tube and taken its IR. After the IR graph was obtained, the peaks were assigned and labeled using a threshold line as the boundary.

Observed Characteristic:

- Yellow-orange color

- Almond-like odor

Specific Functional Group Observed Frequency Vibration (cm-) Intensity Shape

Aldehyde C-H 2815.92 & 2735.25 Medium Weak narrow broad peaks

Aromatic C=C 1455.24 & 1583.05 & 1595.87 Medium Sharp...